The corn kernel, illustrated in FIG. 1, has a number of components, each being best suited for various uses. The process of modern dry corn milling seeks to segregate and separately process the below-identified parts of a kernel of corn as each part has a separate commercial use. The hard outer shell is called the pericarp or the bran coat. The end of the corn kernel which adheres it to the corn cob is called the tip cap. The interior of the corn kernel consists of the endosperm and the germ. The endosperm is generally broken into two parts: soft endosperm and hard endosperm. For purposes of human consumption, the hard endosperm generally produces grits and corn meal, and the soft endosperm generally produces corn flour. The germ contains a much higher percentage of fat compared to the other parts of the kernel and is the source of corn oil.
Of course, dry corn milling is an ancient practice to the human race, dating back many, many years. Historically, mill stones were utilized to grind the corn into meal. Wind- and water-powered mills developed several hundred years ago allowed for increased efficiency in the processing of corn. For the last hundred years, milling operations have utilized roll milling equipment in an effort to separate the components of the corn kernel for more particularized uses.
Modern roll milling equipment utilizes contiguous rollers with varying sized corrugations and varying sized roller gap spacings to grind corn or other grains to achieve the desired particle size fractionation. Typically, mills employ rollers in series with increasingly narrow gaps in a gradual milling process. Through this process, the broken kernels are segregated by size which ideally results in various parts of the corn kernel being segregated and removed to differing processing pathways, often referred to as streams.
Initially, in a typical milling process, after cleaning the hard outer shell, the corn kernel is fractured via a mechanical process thereby freeing and removing the germ from the remaining parts of the kernelxe2x80x94a step called degermination. The remaining parts of the kernel are broken up by the series of rollers. As this material is processed, the hard outer shell (bran) flakes are removed and the remaining inner meat of the kernelxe2x80x94the soft and hard endospermxe2x80x94are ground further as differing product streams pass through the series of rollers and sifters which separate product by particle size. The end products of the dry corn milling operation are bran, grits, meal, flour, and high fat germ.
A flow scheme typical of prior art mills is illustrated in U.S. Pat. No. 5,250,313. In FIG. 5, of the ""313 patent (reproduced herein as FIG. 2), the incoming corn is cleaned, washed, tempered to the appropriate moisture content, fractured or degerminated, and dried. Various designs exist to carry out the step of degermination. For example, the Ocrim(trademark) degerminator uses a spinning rotor having combination blades to operate against a horizontal, perforated cylinder that only allows partial kernels to pass. The rotor and breaker bars are set to break the corn against a spiral rotor bar and a cutting bar. Another known degerminator is the Beall(trademark) degerminator. In the Beall(trademark) degerminator, grinding occurs through an abrasive action of kernel against kernel, and kernel against a nested conical surface and screen. Impact-type degerminators are also used. An example is the Entoletor(trademark) degerminator. The Entoletor(trademark) includes a vertical drive shaft that operates a rotor. Kernels are fed downwardly towards the rotor where they are accelerated outwardly to impact a surrounding liner surface.
Generally, the product from the degerminator is separated into a first stream that is relatively rich in endosperm and a second stream that is relatively rich in germ and bran. Specifically, with reference again to FIG. 2, the degerminated corn is aspirated to effect initial density separation of the fractured kernel. The tailings and liftings from the aspirators are further separated through additional aspiration or the use of gravity tables. In general, bran, whole germ and germ contaminated particles obtained via density separation are lighter than other constituent parts and may be partially removed via gravity separation to be directed through a series of germ rollers and sifters (which may further separate germ from other components for separate processing in an oil recovery process). Separated, primarily endosperm-containing streams from the gravity tables and aspirators may be directed to different break rollers depending on the particle size of the stream. For example, those primarily endosperm-containing streams having smaller particle sizes may be directed past the first and second break rollers, or as illustrated in FIG. 2, beyond to later break rollers.
The xe2x80x9cbreak rollersxe2x80x9d used in a gradual break process typically comprise corrugated rollers having roller gaps that cascade from wider roller gaps for the 1st break roller to more narrow roller gaps for subsequent break rollers. Roller gaps are the spacings between the exterior or xe2x80x9ctipxe2x80x9d portions of the corrugations on opposing rollers. The use of 5 break rollers is typical, and roller gaps may vary depending on the desired finished product. Typical roller gap distances on prior art systems range from about 0.01 to about 0.07 inches, wherein smaller gaps result in finer particles. In general, the break rollers are operated such that opposing corrugated roller faces rotate at differing rates. Most roller corrugation configurations present a sharp edge and a dull edge as determined by the slope of the corrugation surface. Therefore, breaking may occur under a sharp to sharp, sharp to dull, dull to sharp, or dull to dull arrangement of opposing corrugations.
After break rolling, the further-broken particles are separated, typically by a sifting process. From there, larger particles are further rolled in a subsequent break roller (and the further-broken particles are again sifted), or they are passed on to drying or cooling steps or additional sifting steps to isolate finished products (flour, meal, grits, etc.). Typical finished-product requirements may be found generally in 21 CFR xc2xa7xc2xa7137.215-285 (1993). Of course other products may be desired by particular purchasers. The remaining particles that fail to pass the post germ sifting steps are typically sent to a germ handling process (labeled oil recovery in FIG. 2). The finer particles obtained from the germ roller siftings are processed in a manner generally similar to the finer particles from the break rollers.
In years past, all corn was received and milled with the dry miller accepting whatever percentage of the final product that could be derived from the corn. However, in an effort to maximize production of specific food products, today it is desirable to be able to select corn hybrids which have a higher proportion of the desired component. In traditional wet corn processing, the desired components are the soft endosperm and the germ. In traditional dry corn milling operations, the desired component is the hard endosperm.
With the advent of hybrid corns being developed in the 1930s, dry millers began to seek information in advance as to what percentage or yield of grits could be expected from a particular hybrid in the miller""s production facilities. The sources of this information were xe2x80x9ccandlingxe2x80x9d, speculation regarding grain millability characteristics based on agronomic data, and the collection of sample data from actual dry corn milling production runs.
Candling refers to the process of shining a light through a sample of kernels to obtain a very rough estimate of the relative percentage of germ, hard endosperm and soft endosperm in the kernels. Candling therefore is an imprecise method that may, literally, rely on the observation of shadows and which cannot provide detailed information to teach a miller how a given sample will perform in a given mill.
Analysis of grain based on agronomic data requires the observance of physical traits and a great deal of speculation regarding how the particular hybrid may perform in a given milling regime. Neither candling nor the analysis of agronomic data provide any information or data for the miller that relate directly to mill performance characteristics (millability of the corn). Millability characteristics relate not only to what the content of the sample kernels may be, but also to how the sample kernels will perform in a mill. Examples of such data include: the bran coat thickness, the relative ease or difficulty with which the germ may be removed from the endosperm, the relative ease or difficulty with which the bran coat may be removed from the endosperm, whether the bran coat or the endosperm are likely to be removed in large, intact portions or whether they are likely to fracture and contaminate finely ground streams, or how well the black tip cap will adhere to the germ.
All of the above described prior art methods were inefficient and produced highly variable results. In particular, the use of actual dry corn milling production runs demanded the utilization of production resources for substantial periods of time. Most troubling was the fact that the use of actual production facilities to test hybrids, and corn grown under different conditions or in different locations, demanded the processing and monitoring of large quantities of corn. For example, test runs by a known miller have utilized as many as 840,000 pounds of corn for a 24 hour run.
In general, the corn hybrid development process involves the isolation and development of inbred parent lines and the subsequent crossing of parent lines to create new hybrids. Because the development time for parent lines and hybrids are measured in generations or growing seasons, it could take many years to develop a hybrid to the point of commercial release (or to a point where market quantities are available for such tests). For example, given the quantities of corn recited above, it has been necessary to wait as long as seven or more growing seasons before a hybrid could be fully analyzed for milling suitability. Therefore, with traditional corn millability test methods such as production runs, a miller could truly test a hybrid""s suitability for use in a particular milling process only after the hybrid became commercially available. This caused substantial investment by hybrid developers for an extended period of time before millers could even test a new hybrid. Therefore, there has been a need for information flow from the dry corn miller to the hybrid breeders to enable hybrid breeders to make breeding decisions and hybrid development decisions tailored to meet the millers"" specific requirements and product specifications early in the breeding process.
A description of prior patents is provided below. Only approximately 5% of all corn grown is used for human consumption with the remaining 95% of the corn utilized in stock feeds, or in the production of sweeteners and alcohol. As a result, it appears that there has been limited patent activity regarding dry corn milling operations in general, and pilot or test milling operations in particular.
The Pollock patent, U.S. Pat. No. 1,117,963 issued Nov. 17, 1914, describes a method for test milling wheat and other grains. The ""963 patent presents a full scale milling system which employs test chutes into which the product of the milling operation at particular points may be directed. The invention of the ""963 patent relies upon an exact measurement of time to determine the results of the test. At the inception, the grain under test enters the processing system at a timed rate, and then the product of the milling operation can be removed at a corresponding timed rate with determination then made as to the amount of waste and exact proportions of the several products being produced. The ""963 patent therefore relates to the previously described full scale production mill sampling or testing method.
In relation to the current invention, the ""963 test system does not employ an independent test process which allows for a precise determination as to the products of the specific grain hybrid under examination. In addition, the ""963 invention is not a bench scale test, but in fact is a full scale milling system. The only way in which the ""963 system would allow for a determination of the percentage of products from a specific hybrid is to mill large quantities of the specific hybrid and measure the end result of this complete production run. This is highly time consuming and inefficient, and does not allow for the pre-selection of the desired grain or the analysis of pre-commercial hybrids that may only exist in small quantities.
The Anderson patent, U.S. Pat. No. 3,399,839, issued Sep. 3, 1968, describes a dry corn milling process which employs the addition of water for purposes of softening the bran to facilitate removal by an abrasive mechanical method, and to isolate and remove the germ from the kernel. The ""839 patent discloses a milling production technique and does not present a process for the advanced determination of hybrid suitability for milling, or a xe2x80x9csmallxe2x80x9d scale or xe2x80x9cbenchxe2x80x9d scale testing protocol and method.
The Giguere patent, U.S. Pat. No. 5,250,313 issued Oct. 5, 1993, is similar to the ""839 patent in that it describes yet another way to remove the bran and isolate and remove the germ from the corn being processed. It is a full scale production process, and it does not allow for a test or bench scale determination as to the expected end products from the dry milling of the specific hybrid of corn under analysis.
Therefore, there has been and remains a need for a testing method to provide accurate yield and grit production estimates in a short amount of time relative to full scale milling production runs. Also, there has been and remains a need for such a method to determine accurate yield and grit production estimates based on a small or bench scale simulation of the full scale milling process. In addition, there has been and remains a need for a method to identifY those data collection points within the simulation or bench-scale test that are determinative of the desired data, i.e. grit production, meal production, total product yield, etc. Finally, there is a need for a shortened simulation method based on these identified key data points to allow further streamlining of the micro-mill or test protocol by elimination of process steps from the simulation without sacrificing accuracy in the millability analysis. Such a shortened simulation would comprise an expedited lab technique capable of providing accurate millability predictions in a reduced amount of time relative to the longer small scale test simulation. Depending on the number of steps eliminated in the design of the shortened test protocol, up to xc2xd or more of the time required to perform the test may be eliminated.
It is therefore an object of the present invention to provide a shortened protocol and longer protocol small scale xe2x80x9cminiaturexe2x80x9d or xe2x80x9cmicro-millxe2x80x9d simulations that impart the inherent advantages of allowing the test milling and analysis of a small or bench scale quantity of grain. With such small quantities, new corn hybrids may be tested many growing seasons prior to the commercial release of the hybrid. Importantly, this ability to test the milling suitability of pre-commercial hybrids early in the hybrid development process allows dry corn millers and hybrid developers to communicate and collaborate in the selection and development of hybrids for commercial release. Information derived through the pilot scale test milling process may therefore be used not only to help millers select the most beneficial hybrid for their desired process, but to more efficiently direct the hybrid breeding operation to produce grain having the specifically tailored requirements of the miller. This is in stark contrast to earlier attempts to gauge hybrid suitability for milling through the milling of full scale production-run quantities of grain, or through speculation regarding milling suitability based on physically observable traits and other agronomic data.
The present invention relates to a method for simulating a milling process to determine the suitability of grain samples for milling, a method for shortening the simulation protocol without sacrificing accuracy in the determination of suitability for milling, a method for employing the simulation and the shortened simulation to direct input grain selection for the full scale mill that is simulated, and a method for employing the simulation and the shortened simulation to direct hybrid development. The embodiments and advantages described herein are generally described with reference to corn and corn hybrids. However, it is clear that the benefits and advantages of the present invention relate more broadly to the testing and milling of other grains and other products wherein small scale test processing provides useful benefits by allowing early testing of newly developed strains, breeds, hybrids, designs or products, savings through the use of bench scale rather than full scale quantities, and decreasing production facility downtime through the separation of testing equipment from production equipment to avoid the use of production resources for testing purposes.
A small scale test milling process and method for determining anticipated hybrid performance is disclosed. The small scale test milling process allows accurate prediction of total mill yield (lbs. of input raw corn/lbs. of output finished product) and grit extraction percentage (lbs. of grit output/lbs. of raw corn input). The small scale test milling process is a simulation of a selected full scale or commercial milling facility. The small scale test milling process or simulation is referred to herein as the long-protocol test. This test generates accurate predictions for full scale mill performance based on the test milling of small samples (e.g. 1.0 kg of grain) and short time frames relative to full scale processes, which processes may employ tens to hundreds of thousands of pounds of grain depending upon the mill, sampling procedure, and run times.
In addition, the present invention includes a xe2x80x9cshortenedxe2x80x9d small scale test milling process and a method for obtaining a xe2x80x9cshortenedxe2x80x9d small scale test milling protocol based on the analysis of data generated in the long-protocol test milling process. It has been discovered that not only does the long-protocol small scale test milling process and simulation allow accurate prediction of total product yield and total grit extraction, but that key data from key data collection points within the long-protocol small scale test milling process may be identified and simulation process steps may be eliminated without sacrificing accuracy in the test results.
The long-protocol small scale test mill process includes the simulation of selected full scale production mill process stepsxe2x80x94typically the sieving of raw corn, the conditioning of the sieved corn to an appropriate moisture content, the degermination of the conditioned corn, the aspiration of the degerminated or broken corn, the separation or sifting of the aspirated corn by size classes, and subsequent rolling, aspiration, and sifting steps. The sifting and rolling steps employ various roller gaps and mesh wire sizes, and the separated sample fractions from these sifting steps are weighed and recorded.
The shortened test mill process protocols were derived through the application of multiple linear regression analyses to model or fit equations (curves) to the measured data. These analyses revealed that, when testing is performed utilizing a lengthy series of simulation steps (e.g. repeated and gradual roller breaks and siftings) the end results, measured as total production yield and total grit extraction percentage, could be determined from a select few data points. It has therefore been discovered that key points in the simulation process of breaking, rolling and sifting the corn serve as extremely accurate predictors of total yield output and total grit production. As a result, the shortened small scale or test mill process need not employ all the rolling and sifting steps involved in the long-protocol or more complete small scale simulation of the production or full scale mill.
The current invention may utilize the traditional dry milling operation to break the kernels and allow for the removal of the bran. More significantly, it presents a process whereby the content of the hard endosperm, and the grits produced therefrom, can be determined in relation to a specific hybrid of corn. Importantly, because the present invention allows testing of small quantities of hybrid, it is not necessary to wait until commercial release of the hybrid to test its suitability. This may reduce the number of growing seasons that the mill or the hybrid developer must wait for a new hybrid to test, and provide significant information to the hybrid developer so that more focused trait selection may be made in developing the parent corn seed and in crossing that parent with another parent to produce the new hybrid possessing the desired characteristics. Therefore, the present invention also relates to methods for selecting grain and directing hybrid research through application of the simulation processes disclosed herein.